[high-performance two-phase flow evaporator]

ABSTRACT

A high-performance two-phase flow evaporator is disclosed to include an electronic device, a non-metal casing, a heat sink device provided at the topside of the non-metal casing and defining with the non-metal casing an enclosed chamber, a working fluid contained in the enclosed chamber, and a heat conductivity member formed of higher heat conductivity material (k&gt;100 W/m.K) in the bottom side of the non-metal casing and disposed in contact between the electronic device and the working fluid for transferring heat energy from the electronic device to the working fluid to heat the working fluid to give off steam so that heat energy is quickly dissipated from the electronic device into the outside open air through the heat sink device.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates generally to an evaporator and moreparticularly to a high-performance two-phase flow evaporator, whicheffectively dissipates heat energy from an electronic device by mans ofthe continuously alternating phase changing action between vapor phaseand liquid phase of a working fluid.

2. Description of the Related Art

Following fast development of high technology, electronic devices aremade in a mini scale, and have enhanced performance. However, anadvanced electronic device releases much heat energy during operation.High temperature causes an advanced electronic device to release freeelectrons and thermal stress, resulting in working instability andshortening of service life. Therefore, it is important to dissipate heatenergy from a working electronic device for preventing an overheat ofthe working electronic device. Because personal computer is popular andthe life cycle of computer generation is short, the elimination rationof CPU is relatively increased. Improving the function and acceleratingthe speed of a CPU will relatively cause the CPU to produce much heatenergy. Within the surface area of a CPU, the working temperature of aCPU is about 60˜95° C. Continuous working may cause increasing of theworking temperature. Without cooling means to dissipate heat energy mayresult in abnormality of the CPU. Therefore, it is important to improvethe heat dissipation efficient of CPU cooling means.

Under the circumstances in view, two-phase flow evaporator (s) aredeveloped for use to dissipate heat energy from an electronic device. Aconventional two-phase flow evaporator is comprised of a hollow metalcontainer and radiation fins at the topside of the metal container. Whenin use, the bottom wall of the metal container is kept in contact withthe electronic device, enabling heat energy to be transferred from theelectronic device through the bottom wall to the inside of the metalcontainer. The metal container has a capillary structure inside thesurface metal, and the inside space of the metal container is drawn intoa vacuum status. During transferring of heat energy from the electronicdevice to the metal container, a part of heat energy is transmitted tothe whole metal container, and the rest of heat energy is transferredthrough the contact area between the electronic device and the metalcontainer to the inside space of the metal container. Because the insidespace of the metal container is maintained in a vacuum status, theworking fluid in the capillary structure is caused to change the phasewhen hot, i.e., the working fluid is changed from liquid status intovapor status, thereby producing bubbles. Because the inside pressure ofthe bubbles is relatively greater, the bubbles move over the capillarystructure to the space above the capillary structure, and then touch thecold top wall of the metal container. When touching the cold top wall ofthe metal container, heat energy is transferred from vapor to the topwall of the metal container for dissipation into the outside open air bythe radiation fins, and at the same time vapor is condensed into liquid,which is transferred to the hot side by means of the capillary action ofthe capillary structure. Because reversible liquid-vapor phase changeabsorbs or releases a big amount of heat energy, this design oftwo-phase flow evaporator has the characteristic of transferring heatenergy rapidly at a big volume, keeping the working temperature of theelectronic device stable.

Conventionally, a metal container for two-phase flow evaporator is madeby welding two open metal casing together, or welding two metal platesto the two ends of a metal column. Before welding or vacuum process,metal powder may be sintered to form the desired capillary structure. Atwo-phase flow evaporator made according to this design is heavy andexpensive. When installing the retaining devices during assembly of atwo-phase flow evaporator with an electronic device, the metal containermay be deformed, thereby breaking the capillary structure. Damage to thecapillary structure may lower heat transfer efficiency, or cause theworking fluid unable to return to the hot side, thereby resulting in dryout. Further, because heat energy is transmitted from the electronicdevice to the whole metal container, less amount of heat energy istransferred by phase change, the working efficiency of the two-phaseflow evaporator is greatly reduced.

Therefore, it is desirable to provide a high-performance two-phase flowevaporator that eliminates the aforesaid drawbacks.

SUMMARY OF INVENTION

The present invention has been accomplished under the circumstances inview. According to one aspect of the present invention, thehigh-performance two-phase flow evaporator comprises an electronicdevice, a non-metal casing, a heat sink device provided at the top sideof the non-metal casing and defining with the non-metal casing anenclosed chamber, a working fluid contained in the enclosed chamber, anda heat conductivity member formed of higher heat conductivity material(k>100 W/m.K) in the bottom side of the non-metal casing and disposed incontact between the electronic device and the working fluid fortransferring heat energy from the electronic device to the working fluidto heat the working fluid to give off steam so that heat energy isquickly dissipated from the electronic device into the outside open airthrough the heat sink device. According to another aspect of the presentinvention, the casing can be directly injection-molded from plastics onthe heat conductivity member of higher heat conductivity material (k>100W/m.K) to reduce the weight of the evaporator for preventing breaking ordamage of the electronic device due to a heavy load. After molding ofthe casing on the heat conductivity member, the casing is assembled withthe heat sink device. This manufacturing method is practical for massproduction at a high manufacturing speed to reduce the cost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an elevational view of a high-performance two-phase flowevaporator according to the first embodiment of the present invention.

FIG. 2 is an exploded view of the high-performance two-phase flowevaporator according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional side view of the first embodiment of thepresent invention, showing the high-performance two-phase flowevaporator in operation (I).

FIG. 4 is a schematic sectional side view of the first embodiment of thepresent invention, showing the high-performance two-phase flowevaporator in operation (II).

FIG. 5 is a sectional side view of showing the operation of ahigh-performance two-phase flow evaporator according to the secondembodiment of the present invention.

FIG. 6 is a sectional side view of showing the operation of ahigh-performance two-phase flow evaporator according to the thirdembodiment of the present invention.

DETAILED DESCRIPTION

Referring to FIGS. 1˜3, a high-performance two-phase flow evaporator inaccordance with the first embodiment of the present invention is showncomprised of a casing 1, a working fluid 2, and an electronic device 3.

The casing 1 is a non-metal member defining an enclosed chamber 11 foraccommodating the working fluid 2. The inside pressure of the enclosedchamber 11 is lower than the atmospheric pressure, i.e., the enclosedchamber 11 is maintained in a vacuum status. The casing 1 has a heatconductivity member 12 formed of higher heat conductivity material(k>100 W/m.K) in the bottom side of the enclosed chamber 11. The heatconductivity member 12 has a bottom contact surface 121 disposed incontact with the electronic device 3, and a top heating surface 122disposed in contact with the working fluid 2. The topside of theenclosed chamber 11 is a metal heat sink device 13. The heat sink device13 comprises a flat base 131 that closes the topside of the casing 1,and a plurality of radiating fins 132 upwardly extended from the topwall of the flat base 131.

The working fluid 2 is held in the enclosed chamber 11 inside the casing1. The working fluid 2 can be water, alcohol, acetone, or their mixture.

The electronic device 3 is disposed in contact with the bottom contactsurface 121 of the heat conductivity member 12.

Referring to FIGS. 3 and 4, when the electronic device 3 is releasingheat energy during operation, the heat conductivity member 12 absorbsheat energy from the electronic device 3 and transfers absorbed heatenergy to the working fluid 2. Because the casing 1 is made of non-metalmaterial and the heat conductivity member 12 is formed of higher heatconductivity material (k>100 W/m.K), heat energy does not disperse andis gathered at the top heating surface 122 to heat the working fluid 2.By controlling the enclosed chamber 11 in a vacuum status to lower theboiling point of the working fluid 2, the working fluid 2 can be quicklyheated by the top heating surface 122 to give off steam that flowstoward the heat sink device 13 (see hollow arrow signs in FIG. 3),enabling heat energy of steam to be absorbed by the flat base 131 of theheat sink device 13 and than transferred to the radiating fins 132, sothat heat energy can be quickly dissipated into the outside open air.When heat energy of steam was absorbed by the heat sink device 13, steamis condensed into liquid status and returned to the bottom side of theenclosed space 11 due to the effect of gravity or capillary action. (seethe hollow arrow signs in FIG. 4). When returned to liquid status, theworking fluid 2 absorbs heat energy from the top heating surface 122 andis heated to give off steam again. This liquid-vapor phase alternationcontinues, and therefore heat energy is efficiently dissipates from theelectronic device 3 into the outside open air through the heat sinkdevice 13 via the casing 1 and the working fluid 2.

Referring to FIG. 5, the flat base 131 of the heat sink device 13 has acapillary structure 14 that increases the contact area to accelerateliquid-vapor phase changing speed. An electric fan 4 is provided at thetopside of the radiation fins 132 and adapted to cause currents of airtoward the radiation fins 132. Besides, a steam guide device 111 isprovided inside the enclosed chamber 11 and adapted to guide steam fromthe working fluid 2 to the flat base 131 of the heat sink device 13.

Referring to FIG. 6, because the shell of the electric device 3 is madeof higher heat conductivity material and the heat conductivity member 12forms with the casing 1 a recessed hole, the electronic device 3 isdirectly inserted into the recessed hole and firmly secured thereto sothat heat energy from the electronic device 3 can directly heat theworking fluid 2 to give off steam, preventing accumulation of heatenergy in the electronic device 3. Therefore, this design enhances thestability of the electronic device 3 and extends the service life of theelectronic device 3. Further, the electronic device 3 can be a CPU(central processing unit).

Further, the top wall of the flat base 131 of the heat sink device 13can be made having a corrugated or serrated face to increase contactarea to air and to further accelerating condensing of vapor into liquid.The non-metal material of the casing 1 can be plastics or ceramics. Thehigher heat conductivity material (k>100 W/m.K) of the heat conductivitymember 12 can be copper or aluminum alloy, ceramic material such asgraphite, silicon carbide, aluminum nitride, or boron nitride, orcompound material such as aluminum and silicon carbide compound,graphite and copper compound, graphite and aluminum compound. The casing1 can be injection molded from plastics on the heat conductivity member12 of higher heat conductivity material (k>100 W/m.K), and thenassembled with the heat sink device 13 that is extruded from aluminum ormade through a different manufacturing process. This manufacturingmethod is practical for mass production at a high manufacturing speed toreduce the cost.

Further, metal, ceramic, or non-metal balls and/or powder of densityratio higher than the working fluid 2 may be added to the working fluid2 in the enclosed chamber 11 to enhance heat transfer efficiency or tolift the water lever of the working fluid 2 for enabling the heatconductivity member 12 to be fully covered by the working fluid 2without affecting the performance of the heat sink device 13.

In general, the high-performance two-phase flow evaporator of thepresent invention has the following features.

1. The invention provides a heat conductivity member 12 of higher heatconductivity material (k>100 W/m.K) and a metal heat sink device 13 atthe bottom and top sides of the non-metal casing 1 so that released heatenergy from the electronic device 3 can be almost fully absorbed by theheat conductivity member 12 and transferred upwards through the topheating surface 122 to heat the working fluid 2 to give off steam. Dueto minor pressure difference, steam flows upwards to the heat sinkdevice 13, and the heat sink device 13 efficiently transfers heat energyfrom steam to the outside air, causing steam to be quickly condensedinto liquid status. Because heat energy is quickly dissipated from theelectronic device 3 into the outside open air through the working fluid2 and the heat sink device 13, the invention prevents accumulation ofheat energy at the electronic device 3, and therefore enhancing theworking stability of the electronic device 3 and extending the servicelife of the electronic device 3.

2. Because the casing 1 is made of non-metal material, the weight of theevaporator can greatly be reduced, preventing breaking or damage of theelectronic device 3 due to a heavy load. The casing 1 can be directlyinjection-molded from plastics on the heat conductivity member 12, andthen assembled with the heat sink device 13. Therefore, thismanufacturing method is practical for mass production at a highmanufacturing speed to reduce the cost.

Although a particular embodiment of the invention has been described indetail for purposes of illustration, various modifications andenhancements may be made without departing from the spirit and scope ofthe invention. Accordingly, the invention is not to be limited except asby the appended claims.

1. A high-performance two-phase flow evaporator comprising: anelectronic device; a non-metal casing mounted on said electronic deviceat a topside; a metal heat sink device provided at a topside of saidnon-metal casing and defining with said non-metal casing an enclosedchamber; a working fluid contained in said enclosed chamber; and a heatconductivity member formed of higher heat conductivity material (k>100W/m.K) in a bottom wall of said non-metal casing, said heat conductivitymember having a bottom contact surface disposed in contact with saidelectronic device and adapted to absorb heat energy from said electronicdevice during operation of said electronic device and a top heatingsurface disposed in contact with said working fluid and adapted totransfer heat energy from said bottom contact surface to said workingfluid to heat said working fluid.
 2. The high-performance two-phase flowevaporator as claimed in claim 1, wherein said heat conductivity memberdefines with said non-metal casing a recessed hole that accommodatessaid electronic device.
 3. The high-performance two-phase flowevaporator as claimed in claim 1, wherein said electronic device is aCPU (central processing unit).
 4. The high-performance two-phase flowevaporator as claimed in claim 1, wherein said metal heat sink devicecomprises a flat base that covers a top side of said non-metal casing,and a plurality of radiation fins upwardly extended from a top wall ofsaid flat base.
 5. The high-performance two-phase flow evaporator asclaimed in claim 4, wherein said flat base of said heat sink device hasa corrugated top surface to increase contact area and to furtheraccelerating condensing of steam in fluid.
 6. The high-performancetwo-phase flow evaporator as claimed in claim 4, wherein said flat baseof said heat sink device has a serrated top surface to increase contactarea and to further accelerating condensing of steam in fluid.
 7. Thehigh-performance two-phase flow evaporator as claimed in claim 4,wherein said radiating fins further comprise an electric fan.
 8. Thehigh-performance two-phase flow evaporator as claimed in claim 4,wherein said flat base has a capillary structure in a top surfacethereof to increase the contact area to accelerate liquid-vapor phasechanging speed.
 9. The high-performance two-phase flow evaporator asclaimed in claim 1, wherein said enclosed chamber further comprise asteam guide means and adapted to guide steam from said working fluid tosaid heat sink device.
 10. The high-performance two-phase flowevaporator as claimed in claim 1, wherein said non-metal casing is madeof plastics.
 11. The high-performance two-phase flow evaporator asclaimed in claim 1, wherein said non-metal casing is made of ceramics.12. The high-performance two-phase flow evaporator as claimed in claim1, wherein said higher heat conductivity material (k>100 W/m.K) of saidheat conductivity member is a metal material selected from a metalmaterial group including simplex element and complex of silver, copperand aluminum.
 13. The e high-performance two-phase flow evaporator asclaimed in claim 1, wherein said higher heat conductivity material(k>100 W/m.K) of said heat conductivity member is selected from amaterial groups including graphite, silicon carbide, aluminum nitride,boron nitride, aluminum and silicon carbide complex, graphite and coppercomplex, graphite and aluminum complex.